Method for preparing ultra-pure palladium nitrate through catalytic ozonation

Abstract

The invention discloses a method for preparing ultra-pure palladium nitrate through catalytic ozonation, and relates to a process for preparing a noble metal catalyst through a gas phase oxidation method. The method comprises the following steps: dispersing precious metal palladium or sponge palladium in a proper amount of water to prepare palladium-containing precious metal turbid liquid; industrial waste gas and ozone are introduced into the palladium-containing precious metal turbid liquid, and stirring reaction is conducted for a period of time at the normal temperature; filtering the reacted palladium nitrate solution under the condition that the temperature is not lower than 15 DEG C; the filtered liquid is gradually concentrated under the heating condition, and the palladium nitrate solution with the precious metal concentration not higher than 25 wt% is prepared. Compared with the existing process route, the method has the advantages that the waste nitric oxide is recycled to replace commercial chemicals, the palladium nitrate is efficiently prepared at low cost through the gas-liquid two-phase mixed system reaction in the production process, and the obtained palladium nitrate catalyst is free of external medicament impurities, ultrahigh in purity and good in uniformity.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering, and particularly to a method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation. Background Art

[0002] As an important noble metal catalyst, palladium nitrate has a wide range of applications in various organic synthesis catalytic reactions, electronic components, corrosion-resistant material science, anti-cancer and anti-inflammatory drug medicine, and environmental protection fields. According to the market special analysis of the palladium nitrate industry, due to its extremely high chemical catalytic activity and wide application fields, the industrial demand for palladium nitrate will increase year by year in the future, especially for ultra-high purity palladium nitrate of 4N grade and above. Ultra-high purity palladium nitrate needs to go through multiple processes during industrial preparation. Traditionally, palladium nitrate is mainly prepared by dissolving palladium with aqua regia or reacting nitric acid with palladium salt precursors. These methods have various problems, such as high cost, high environmental pollution, generation of waste, high impurity content, low palladium dissolution rate, etc. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation. The present invention makes full use of industrial waste nitrogen oxide gas, and introduces it into a suspension containing noble metal palladium together with ozone gas, realizing the efficient dissolution of noble metals at room temperature, while avoiding the introduction of other impurities, thereby preparing an ultra-high purity palladium nitrate catalyst solution. The preparation process of the present invention is not only environmentally friendly, but also realizes the recycling of industrial waste gas, reduces production costs, and greatly increases the dissolution rate of noble metal palladium.

[0004] The present invention is achieved by the following technical solutions.

[0005] A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation, comprising the following steps:

[0006] S1. Dispersion: Disperse noble metal palladium or sponge palladium in an appropriate amount of water to prepare a noble metal suspension containing palladium;

[0007] S2. Oxidation: Introduce industrial waste gas and ozone into the noble metal suspension containing palladium respectively, and stir and react at room temperature for a period of time;

[0008] S3. Heat preservation and filtration: Filter the palladium nitrate solution after the reaction in step S2 under the condition of not less than 15 °C;

[0009] S4. Concentration: The liquid obtained after filtration in step S3 is gradually concentrated under heating conditions to prepare a palladium nitrate solution with a noble metal concentration not higher than 25 wt%. In this application, palladium nitrate solutions with different noble metal concentration gradients can be obtained by controlling the solution temperature and the concentration evaporation rate. The crystalline product containing free water is dried in a vacuum drying oven at low temperature and low pressure to obtain a palladium nitrate solid containing crystal water.

[0010] Further, in step S1, the mass concentration of the noble metal suspension containing palladium prepared is 5 wt% - 15 wt%.

[0011] Further, in step S2, the flow rate of ozone is 0.1 Nm 3 -240 Nm 3 .

[0012] Further, in step S2, the flow rate of the industrial waste gas is 10 Nm 3 -360 Nm 3 .

[0013] Further, in step S2, the industrial waste gas is from the by-product gas in the industrial production process or the industrial waste gas of nitric acid production enterprises. The nitrogen oxides in the industrial waste gas are not less than 5 vol%, and the industrial waste gas needs to be pre-filtered 5 times through an industrial filter valve core.

[0014] Further, in step S2, the industrial waste gas and ozone are introduced into the reaction system through an atomizer for dissolution and reaction.

[0015] Further, in step S2, the reaction temperature is not less than 15 °C.

[0016] Further, in step S2, the stirring speed is maintained at 600 - 1200 r / min and the reaction lasts for at least 10 min.

[0017] Further, in step S3, the palladium nitrate solution is filtered through a 0.45-micron filter paper.

[0018] Further, in step S4, the filtered liquid is heated and concentrated between 40 °C and 75 °C.

[0019] This application has the following beneficial effects.

[0020] The present invention provides an environmentally friendly, efficient and low-cost method for preparing a palladium nitrate catalyst by ozone catalytic oxidation and using industrial production waste nitrogen oxide gas. The key advantages and innovations of this method are as follows:

[0021] (1) Environmental protection: Using ozone and the waste nitrogen oxides generated industrially to prepare palladium nitrate can minimize the risk of environmental pollution by harmful substances, and at the same time, the waste resources can be fully utilized to be converted into high-value-added products;

[0022] (2) High efficiency: By precisely controlling the ozone flow rate and reaction conditions, and making full use of waste nitrogen oxides, the preparation efficiency of palladium nitrate can be improved, reducing energy consumption and waste generation;

[0023] (3) Low cost: This method utilizes waste nitrogen oxides in industry, reducing raw material costs and being applicable to cost-sensitive production fields;

[0024] (4) Consistency and quality stability: By precise control, the uniformity of the obtained palladium nitrate solution is ensured, thus ensuring the product quality. In addition, since the preparation and production process of palladium nitrate is through gas-liquid reaction, the total content of base metal impurities in palladium nitrate is almost zero. The strong oxidizing properties of ozone and nitrogen oxides ensure the complete dissolution of noble metal palladium in a single time, guaranteeing the preparation of noble metal palladium at 4N level and above. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the preparation of ultra-high purity palladium nitrate in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following further describes this patent application in conjunction with embodiments.

[0027] Example 1

[0028] A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation, comprising the following steps:

[0029] Take 500 g of noble metal palladium and mix it with 1.5 L of deionized water, and use a mechanical stirrer to mix under the condition of 1200 r / min. Industrial waste gas (nitrogen oxides 15.1 vol%) is passed into the reactor after five-stage industrial filtration, and the flow rate is controlled at 120 N / m 3 , ozone is directly prepared by an industrial ozone generator, and its flow rate is controlled at 40 N / m 3 , and the catalytic reaction is carried out at 22 °C. The mechanical stirrer maintains a stirring speed of 1200 r / min and reacts for 10 min to obtain a palladium nitrate solution. The obtained palladium nitrate solution is subjected to heat preservation filtration at 50 °C, and the filtrate is subjected to constant temperature evaporation and concentration. When trace crystals appear, stop heating and concentration, and use the residual heat for further crystallization. The water-containing crystals after crystallization are placed in a drying oven and dehydrated at 60 °C.

[0030] Example 2

[0031] A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation, comprising the following steps:

[0032] Take 500 g of precious metal palladium and mix it with 1.5 L of deionized water, and use a mechanical stirrer to mix it under the condition of 600 r / min. Industrial waste gas (nitrogen oxides 6.7 vol%) is passed through five-stage industrial filtration and then introduced into the reactor, and the flow rate is controlled at 150 N / m 3 , ozone is directly prepared by an industrial ozone generator, and its flow rate is controlled at 30 N / m 3 , and a catalytic reaction is carried out at 25 °C. The mechanical stirrer maintains a stirring speed of 800 r / min and reacts for 10 min to obtain a palladium nitrate solution. The obtained palladium nitrate solution is filtered while keeping warm at 80 °C, and the filtrate is evaporated and concentrated at a constant temperature. When a small amount of crystals appear, stop heating and concentrating, and use the remaining heat for further crystallization. The water-containing crystals after crystallization are placed in a drying oven and dehydrated at 60 °C.

[0033] The analysis results of the precious metal content of the dried sample are shown in the following table

[0034]

[0035] Example 3

[0036] A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation, comprising the following steps:

[0037] Take 500 g of precious metal palladium and mix it with 1.5 L of deionized water, and use a mechanical stirrer to mix it under the condition of 600 r / min. Industrial waste gas (nitrogen oxides 9.2 vol%) is passed through five-stage industrial filtration and then introduced into the reactor, and the flow rate is controlled at 100 N / m 3 , ozone is directly prepared by an industrial ozone generator, and its flow rate is controlled at 42 N / m 3 , and a catalytic reaction is carried out at 25 °C. The mechanical stirrer maintains a stirring speed of 800 r / min and reacts for 10 min to obtain a palladium nitrate solution. The obtained palladium nitrate solution is filtered while keeping warm at 60 °C, and the filtrate is evaporated and concentrated at a constant temperature. When a small amount of crystals appear, stop heating and concentrating, and use the remaining heat for further crystallization. The water-containing crystals after crystallization are placed in a drying oven and dehydrated at 60 °C.

[0038] The present invention provides a method for rapidly synthesizing high-purity palladium nitrate from industrial waste nitrogen oxides in a gas-liquid phase. This method uses a pure gas-phase catalytic system, recycles industrial by-product waste gas, reduces the risk of environmental pollution in production, and can prepare ultra-high purity and highly homogeneous palladium nitrate precious metal compounds by precisely controlling the gas flow rate.

[0039] The embodiments of the present specific implementation manners are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention shall be covered within the protection scope of the present invention.

Claims

1. A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation, characterized in that: The following steps are involved: S1. Dispersion: Disperse the precious metal palladium or sponge palladium in an appropriate amount of water to prepare a precious metal suspension containing palladium; S2. Oxidation: respectively passing industrial waste gas and ozone into the precious metal suspension containing palladium, stirring and reacting at room temperature for a period of time; S3. Insulation filtration: The palladium nitrate solution after the reaction in step S2 is filtered at a temperature not lower than 15 ° C; S4. Concentration: The liquid obtained after filtering in step S3 is gradually concentrated under heating conditions to prepare a palladium nitrate solution with a noble metal concentration not higher than 25 wt %.

2. A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S1, the mass concentration of the palladium-containing precious metal suspension obtained is 5wt%-15wt%.

3. A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, the ozone flow rate is 0.1Nm 3 -240Nm 3 .

4. A method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, the flow rate of industrial waste gas is 10Nm 3 -360Nm 3 .

5. The method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, the industrial waste gas comes from by-product gas in the industrial production process or industrial waste gas from nitrate-making enterprises. The nitrogen oxides in the industrial waste gas are not less than 5 vol%. The industrial waste gas needs to be filtered through an industrial filter valve core in advance for 5 levels.

6. The method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, industrial waste gas and ozone are introduced into the reaction system through an atomizer to dissolve and react.

7. The method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, the reaction temperature is not less than 15°C.

8. The method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S2, the stirring speed is maintained at 600-1200 r / min and the reaction is carried out for at least 10 minutes.

9. The method for preparing ultra-high purity palladium nitrate by ozone catalytic oxidation according to claim 1, characterized in that: In step S4, the filtered liquid is heated and concentrated at a temperature between 40°C and 75°C.

Images